1. Field of the Invention
This invention relates to field access type magnetic bubble domain devices and is particularly directed to a planar, magnetoresistance, thin film probe for measuring the magnetic field in the plane of the magnetic film.
2. Description of the Prior Art
As is well known in magnetic bubble domain devices or circuits, a magnetic bias field (H.sub.B) is required to maintain the bubble domains stable in the magnetic layer. A rotating magnetic field (H.sub.R) is also required to propagate the domains around the propagation tracks, e.g. the familiar T-bar, I-bar, Y-bar, chevron or similar permalloy elements arranged on the surface of the magnetic layer. The magnetic bias field is usually applied generally orthogonally to the magnetic layer. However, the bias field frequently has an associated in-plane component due to misalignment of the device package in the bias structure. In many instances, the "tilt" of the bias field is desirable and built into the device. For some component configurations, the operating margin may be sensitive to this in-plane (dc) field component. This dc field component also effects the turn-off of the rotating field. That is, any overshoot in the turn-off of the rotating field will reverse the magnetization of the permalloy elements in the memory tracks causing the magnetic domains to drift away or even collapse. By controlled tilt of the bias field, with respect to the device plane, the effect of rotating overshoot can be compensated. Reference is made, for example, to U.S. Pat. No. 3,744,042, by L. S. Cutler et al. for "Memory Protect For Magnetic Bubble Memory".
Thus, it is desirable to have precise information regarding the alignment of the bias field with respect to the device plane in order to enhance the operation of field access bubble devices.
Currently, a conventional semiconductor Hall effect probe is used for measuring the magnetic field component perpendicular to the probe surface. To measure the in-plane component due to vertical misalignment, the semiconductor Hall probe must be arranged perpendicular to the in-plane component itself. Moreover, the semiconductor Hall probe requires costly sophisticated supporting electronics, is physically not feasible to incorporate in a bubble memory system and does not exhibit sufficient sensitivity to detect small misalignments.